FI65265C - FOERFARANDE FOER FRAMSTAELLNING AV VISKOS - Google Patents

Description

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Patent oeddelat N v (51) K ».ik.3 / int.a. 3 c 08 B 9/00 ENGLISH I - Fl N LAN D (21) P «t * nttlh« k * mu * —Pit «nun *« knln | 79331 ^ (22) Htkamlspllvt - Ameknlngtdag 25 * 10.79 ^ ^ (23) AlkupUvi - Glltlghtttdag 25.10.79 (41) Become public - Bllvlt offsntllg 28.0U.80

National Board of Patents and Registration Niht «vik.ipu» n j. date of publication

Patent- och reglstentyreleen Arnokin uttagd och uti. * Krift * n pubiicarad 30.12.83 (32) (33) (31) etuoikeus - Begird prioHtet 27.10.78

German Democratic Republic-Democratic Republic of Germany (DD) WP 208 708 (71) VEB Filmfabrik Wolfen, UUU Wolfen 1, German Democratic Republic-Democratic Republic of Germany (DD) (72) Klaus Fischer, Wolfen, Martin Wilke, Halle, Wilfried Goldberg, Löbejun, Horst Sendner, Wolfen, German Democratic Republic-Democratic Republic of Germany (DD) (7U) Oy Borenius & C: o Ab (5 ^) Method for producing viscose - Förfarande för framställning av Viskos

The invention relates to a process for the production of viscose from cellulose.

When preparing viscose using cellulose as a starting material, the first step is the production of alkali cellulose. In this case, the procedure is generally as follows: The cellulose used as starting material is alkalized either as mash or in strips with 17 to 22% NaOH solution. Excess NaOH solution is removed by pressing so that the resulting early cellulose has a NaOH content of 15 to 17%. The cellulose content of alkali cellulose is 30 .. .35%. The resulting early cellulose is defibered and subjected to oxygen at 20 to .60 ° C until the average molecular size of the cellulose decreases to the desired size due to chain decompositions.

Faster depolymerization at elevated temperatures can be accelerated by the use of oxidants or catalysts such as cobalt or manganese salts. A disadvantage of this type of procedure is the significant proportion of free alkali in early isellulose. Thus, carbon disulphide is consumed not only in the main reaction, for the xanthanization of carbohydrates, but also in side reactions with the alkali free of alkali cellulose, which carbon dioxide is thus not available for esterification. According to DD 75636, this disadvantage is eliminated by double alkali by adding a second alkalization with less than 15% NaOH solution after the initial maturation.

The disadvantage is that, compared with the conventional method, a double alkalizing device is necessary and the associated high investment and operating costs. Furthermore, considerable immersion losses of the small molecule constituents formed in the initial ripening due to their high detachment cannot be avoided.

It is known from DE-A-2 208 335 that wood is treated with energy-rich rays before leaching. The aim of the method is to convert lignin in wood cellulose or hemicellulose. In this case, connections take place between the long molecular chains of wood and fragments of other molecular constituents, in particular between lignin fragments and hemifragments. The result is unbleached cellulose with a higher yield but a higher lignin content. A disadvantage of this method is the increased use of bleaching chemicals in the manufacture of bleached cellulose.

According to DD 113,581 and DD 125,429, the disadvantage of a high proportion of lignin in unbleached cellulose is eliminated by pretreatment with bisulphite or sulphite solutions before irradiation with energy-rich rays. In this case, the lignin content is reduced below the hitherto known level.

The object of the invention is to provide activation of cellulose by means of irradiation. During the cooking and bleaching process, the wood impurity, lignin, is removed, which is promoted by the irradiation of the wood prior to this process, as disclosed in DD 113,585 and DD 125,429. Thus, the radiation collector present in natural or pre-sulfonated form is absent from the cellulose, so that the intended depolymerization, with simultaneous fluffing of the structure, is possible by irradiation of the cellulose.

3 65265

The invention is characterized in that it uses a combination of pre-alkali irradiation of cellulose with energy-rich rays, mainly energy-rich electrons at a radiation dose of 1 to 30 kGy, treatment with a NaOH solution having a concentration of less than 19%, preferably less than 16%, and an alkali solution. sulfidation to xanthogenate after separation.

The radiation dose used is selected so as to obtain the desired average degree of polymerization after alkalization. The advantages of the process according to the invention are that, by means of the irradiation of the cellulose, the preactivation takes place simultaneously with the flocculation and depolymerization of the structure. Thus, alkalization at low lye concentrations is guaranteed and the initial maturation used so far can be omitted. Sulfur carbon, caustic soda and sulfuric acid are further saved.

As a result of the reduced use of CS2, the environment is less stressed by E ^ Ss and CS2iHa. Compared to double alkalinization, there are smaller immersion losses. Since no second alkalizing device or initial ripening is required, operating costs are reduced. The investment input is significantly reduced and less labor is needed.

Performance examples:

Example 1

Beech sulphite cellulose with an average degree of polymerisation of 810 is preactivated by irradiation with electron beams of 10 kGi and decomposed to an average degree of polymerisation of 425. Subsequent immersion alkali is carried out with a 16% solution of NaOH-1 at 21 ° C. Immediately after squeezing out the excess sodium hydroxide solution, sulphidation is started without initial ripening, which lasts for 150 minutes at a temperature of 21 to 29 ° C upwards. The resulting xanthate is dissolved in a centrifugal solvent. The composition of the viscose obtained is 8% cellulose, 5.8% alkali and 28% sulfur carbon relative to cellulose.

The filtration value of this viscose is kw * 967.

Claims (2)

A process for the production of viscose from cellulose, characterized in that a combination of pre-alkali irradiation of the cellulose with energy-rich rays, in particular energy-rich electrons, at a radiation dose of 1 to 30 kGy, is treated with a NaOH solution having a concentration of less than 19%, preferably 16%, as well as sulfation to xanthogenate after separation of the alkali solution. 1. For use in the manufacture of cellulose components, in the case of cellulose, the combination of the original energy cellulose with the cellulose of the energy cell, the energy of the electron cell, the color of the energy is 1 ... 30 NaOH-lösning, the concentration of which is less than 19%, for a total of 16%, and then the alkali-free genomic sulphidering to xanthate.